Fortunately, you don't have to worry about the batteries that are already installed in the devices you're bringing. The TSA has said it's safe to check in items like a laptop or iPhone that already have the batteries in place.

The agency said that loose lithium batteries not installed in devices pose a fire risk to passenger planes. Recently, the National Transportation Safety Board could not rule out the possibility that lithium batteries started a fire in a plane at the Philadelphia National Airport last year, according to the Associated Press.

If you do plan on bringing spare batteries in your carry-on bag, be aware of some other rules: You can only bring batteries with an equivalent of up to 8 grams of lithium content. (Most batteries for cell phones and laptops meet this requirement.) And for lithium metal batteries, whether carried as a spare or installed in a device, batteries are limited to 2 grams of lithium metal.

About the author

Desiree Everts DeNunzio is a freelance editor and writer. She's dabbled in digital media and technology for the past decade, including stints at CNET News and Wired magazine. When she's not fiddling with various gadgets, she spends her time running after chickens and her own brood.
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